Intermediate 5 was trapped as a THF adduct,(f-Bu3SiNH) 2-(THF) Zr= NSi-t-Bu3 (6,> 95%,'H NMR; 81% yield), 24 when the phenyl complex 3 was heated for 45 min in THF. The intermediacy of bis (amido) imido 5 is also consistent with the deuteration of amido protons during the course of C6D6 ac-tivation. During the thermolysis of (f-Bu3SiNH) 3ZrCH3 (2) in

C6D6, a single NH resonance of the phenyl derivative was observed (‘H NMR) to grow in and then recede. Bymonitoring this signal, attributed to intermediates (f-Bu3SiNH) 2 (t-Bu3SiND) ZrC6D5 (3-(ND)-rfs) and (f-Bu3SiNH)(l-Bu3SiND) 2ZrC6D5 (3-(ND) 2-rf5), the rate constant for elimination of C6D5H from the latter can be determined (96.6 C, k= 7.1 X 10" 4 s'* 1*) by using the methane extrusion rate above. 25 Consistent with thisobservation is the rate of C6H6 elimination (96.7 C, kPhH= 2.26 (2) X 10~ 3 s'1) from (/-Bu3SiNH) 3ZrPh (3) in C6D6, which is three times faster due to the statistical factor ascribed to the three amido protons.